Method for producing organic electroluminescent display device

ABSTRACT

An organic EL display device ( 100 ) including a plurality of pixels includes an element substrate ( 1 ) including a substrate, and a plurality of organic EL elements supported by the substrate and respectively located in the plurality of pixels; and a thin film encapsulation structure ( 10 ) covering the plurality of pixels. The thin film encapsulation structure includes a first inorganic barrier layer ( 12 ), an organic barrier layer ( 14 ) in contact with a top surface of the first inorganic barrier layer ( 12 ), the organic barrier layer ( 14 ) including a plurality of solid portions distributed discretely, and a second inorganic barrier layer ( 16 ) in contact with the top surface of the first inorganic barrier layer ( 12 ) and top surfaces of the plurality of solid portions of the organic barrier layer ( 14 ). The organic barrier layer ( 14 ) is black.

TECHNICAL FIELD

The present invention relates to an organic EL display device and amethod for producing the same.

BACKGROUND ART

Organic EL (Electro-Luminescence) display devices start being put intopractical use. One feature of an organic EL display device is beingflexible. An organic EL display device includes, in each of pixels, atleast one organic EL element (Organic Light Emitting Diode: OLED) and atleast one TFT (Thin Film Transistor) controlling an electric current tobe supplied to each of the at least one OLED. Hereinafter, an organic ELdisplay device will be referred to as an “OLED display device”. Such anOLED display device including a switching element such as a TFT or thelike for each of OLEDs is called an “active matrix OLED display device”.A substrate including the TFTs and the OLEDs will be referred to as an“element substrate”.

An OLED (especially, an organic light emitting layer and a cathodeelectrode material) is easily influenced by moisture to be deterioratedand to cause display unevenness. One technology developed in order toprovide an encapsulation structure that protects the OLED againstmoisture while not spoiling the flexibility of the OLED display deviceis a thin film encapsulation (TFE) technology. According to the thinfilm encapsulation technology, an inorganic barrier layer and an organicbarrier layer are stacked alternately to provide a sufficient level ofbarrier property against water vapor with these thin films. From thepoint of view of the moisture-resistance reliability of the OLED displaydevice, such a thin film encapsulation structure is typically requiredto have a WVTR (Water Vapor Transmission Rate) lower than, or equal to,1×10⁻⁴ g/m²/day.

A thin film encapsulation structure used in OLED display devicescommercially available currently includes an organic barrier layer(polymer barrier layer) having a thickness of about 5 μm to about 20 μm.Such a relatively thick organic barrier layer also has a role offlattening a surface of the element substrate. However, such a thickorganic barrier layer involves a problem that the bendability of theOLED display device is limited.

Patent Document No. 1 discloses a thin film encapsulation structureincluding a first inorganic material layer, a first resin member and asecond inorganic material layer provided on the element substrate inthis order, with the first inorganic material layer being closest to theelement substrate. In this thin film encapsulation structure, the firstresin member is present locally, more specifically, around a protrudingportion of the first inorganic material layer (first inorganic materiallayer covering a protruding portion). According to Patent Document No.1, the first resin member is present locally, more specifically, aroundthe protruding portion, which may not be sufficiently covered with thefirst inorganic material layer. With such a structure, entrance ofmoisture or oxygen via the non-covered portion is suppressed. Inaddition, the first resin member acts as an underlying layer for thesecond inorganic material layer. Therefore, the second inorganicmaterial layer is properly formed and properly covers a side surface ofthe first inorganic material layer with an expected thickness. The firstresin member is formed as follows. An organic material heated andvaporized to be mist-like is supplied onto an element substratemaintained at a temperature lower than, or equal to, room temperature.The organic material is condensed and put into liquid drops on thesubstrate. The organic material in liquid drops moves on the substrateby a capillary action or a surface tension to be present locally, morespecifically, at a border between a side surface of the protrudingportion of the first inorganic material layer and a surface of thesubstrate. Then, the organic material is cured to form the first resinmember at the border. Patent Documents Nos. 2 and 3 also disclose anOLED display device including a similar thin film encapsulationstructure.

The thin film encapsulation structure, described in each of PatentDocuments Nos. 1 and 2, including an organic barrier layer formed of aresin member that is present locally does not include a thick organicbarrier layer, and therefore, is considered to improve the bendabilityof the OLED display device.

CITATION LIST Patent Literature

Patent Document No. 1: WO2014/196137

Patent Document No. 2: Japanese Laid-Open Patent Publication No.2016-39120

Patent Document No. 3: Japanese Laid-Open Patent Publication No.2015-50022

SUMMARY OF INVENTION Technical Problem

The OLED display device, produced by the method described in each ofPatent Documents Nos. 1 and 2, including a thin film encapsulationstructure including an organic barrier layer that includes a pluralityof solid portions distributed discretely is not necessarily consideredto be provided at a high yield.

As described above, in the case where an organic barrier layer is formedby the method described in Patent Document No. 1 or 2, if a surface ofthe first inorganic material layer includes a protruding portion, theorganic barrier layer (solid portion) may be formed only around theprotruding portion of the surface of the first inorganic material layer.However, the method for forming the organic barrier layer described inPatent Document No. 1 or 2 merely uses a surface tension of the resin ina liquid state to form the organic barrier layer locally. Therefore, theorganic barrier layer may not be formed with certainty in a region wherethe organic barrier layer needs to be formed. Oppositely, the organicbarrier layer may be formed in a region where the organic barrier layerdoes not need to be formed. The organic barrier layer in the thin filmencapsulation structure described in Patent Document No. 1 or 2 isformed of a transparent photocurable resin. Therefore, it is not easilychecked whether or not the organic barrier layer is properly formedaround the protruding portion of the surface of the first inorganicmaterial layer. In other words, it requires time and/or cost to inspectwhether or not the organic barrier layer is formed in a region where theorganic barrier layer needs to be formed.

The protruding portion of the surface of the first inorganic materiallayer is formed by a stepped portion reflecting a line such as, forexample, a gate bus line, a source bus line, a lead wire connected withthe gate bus line or the source bus line, or the like. Also in the casewhere a particle (microscopic dust particle) is present above or belowthe first inorganic material layer, the protruding portion is formed atthe surface of the first inorganic material layer.

The present invention, made to solve the above-described problems, hasan object of providing an organic EL display device including a thinfilm encapsulation structure, and a method for producing the same, thatimprove the yield.

Solution to Problem

An organic EL display device according to an embodiment of the presentinvention is an organic EL display device including a plurality ofpixels. The organic EL display device comprises an element substrateincluding a substrate, and a plurality of organic EL elements supportedby the substrate and respectively located in the plurality of pixels;and a thin film encapsulation structure covering the plurality ofpixels. The thin film encapsulation structure includes a first inorganicbarrier layer, an organic barrier layer in contact with a top surface ofthe first inorganic barrier layer, the organic barrier layer including aplurality of solid portions distributed discretely, and a secondinorganic barrier layer in contact with the top surface of the firstinorganic barrier layer and top surfaces of the plurality of solidportions of the organic barrier layer. The organic barrier layer isblack.

In an embodiment, the organic barrier layer contains a dye or a pigment.

In an embodiment, the organic EL display device further includes a banklayer defining each of the plurality of pixels. The bank layer has aninclining surface enclosing each of the plurality of pixels, and theplurality of solid portions include a pixel periphery solid portionextending on the first inorganic barrier layer from an inclining surfacethereof to a peripheral area in the pixel.

In an embodiment, the inclining surface of the bank layer has aninclination angle smaller than, or equal to, 60 degrees.

A production method according to an embodiment of the present inventionis a method for producing any one of the above-described organic ELdisplay devices. A step of forming the thin film encapsulation structureincludes step A of preparing the element substrate having the firstinorganic barrier layer formed thereon, step B of forming a liquid filmcontaining a photosensitive resin on the first inorganic barrier layer,step C of irradiating the liquid film with light to form a resin layer,and step D of forming the organic barrier layer, the step D includingthe step of partially removing the resin layer by a dry process.

In an embodiment, the inclining surface of the first inorganic barrierlayer is lyophilic to the liquid film, and a region enclosed by the banklayer is repelling against the liquid film.

In an embodiment, the step D further includes the step of performing aplasma process and/or a corona process.

In an embodiment, the step of forming the thin film encapsulationstructure further includes the step of, after the step A and before thestep B, performing asking on a surface of the first inorganic barrierlayer.

In an embodiment, the step of forming the thin film encapsulationstructure further includes the step of, after the step A and before thestep B, supplying a silane coupling agent onto the surface of the firstinorganic barrier layer.

In an embodiment, the liquid film contains a photocurable resin and adye or a pigment.

In an embodiment, the liquid film contains a photopolymerizable dyemonomer.

In an embodiment, the step B is performed by spraying, spin-coating,slit-coating, screen printing or inkjet printing.

In an embodiment, the step B includes the steps of, after the step A,putting the element substrate into a chamber and supplying a vapor-likeor mist-like photocurable resin into the chamber, and condensing thephotocurable resin on the first inorganic barrier layer to form theliquid film.

In an embodiment, the production method further includes the steps of,after the step of forming the thin film encapsulation structure,optically acquiring a pattern of the organic barrier layer, anddetermining whether the thin film encapsulation structure is good or notbased on the pattern.

Advantageous Effects of Invention

An embodiment of the present invention provides an organic EL displaydevice including a thin film encapsulation structure, and a method forproducing the same, that improve the yield.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) is a schematic partial cross-sectional view of an activeregion of an OLED display device 100 according to an embodiment of thepresent invention, and FIG. 1(b) is a partial cross-sectional view of aTFE structure 10 formed on an OLED 3.

FIG. 2 is a plan view schematically showing a structure of the OLEDdisplay device 100 according to an embodiment of the present invention.

FIG. 3(a) through FIG. 3(c) are each a schematic cross-sectional view ofthe OLED display device 100; FIG. 3(a) is a cross-sectional view takenalong line 3A-3A′ in FIG. 2, FIG. 3(b) is a cross-sectional view takenalong line 3B-3B′ in FIG. 2, and FIG. 3(c) is a cross-sectional viewtaken along line 3C-3C′ in FIG. 2.

FIG. 4(a) is an enlarged view of a portion including a particle P shownin FIG. 3(a), FIG. 4(b) is a schematic plan view showing the sizerelationship among the particle P, a first inorganic barrier layer (SiNlayer) covering the particle P, and an organic barrier layer, and FIG.4(c) is a schematic cross-sectional view of the first inorganic barrierlayer covering the particle P.

FIG. 5 is a plan view schematically showing a plurality of pixels and abank layer 48 included in the OLED display device 100.

FIG. 6(a) and FIG. 6(b) are each a schematic cross-sectional view of theOLED display device 100; FIG. 6(a) is a cross-sectional view taken alongline 6A-6A′ in FIG. 5, and FIG. 6(b) is a cross-sectional view takenalong line 6B-6B′ in FIG. 5.

FIG. 7 is a schematic view showing a foreign object detection device 50usable for a method for producing an OLED display device according to anembodiment of the present invention.

FIG. 8 is a schematic view showing an inkjet device 60 usable for themethod for producing an OLED display device according to an embodimentof the present invention.

FIG. 9 shows schematic views provided to describe a preferred range ofvolume of an organic barrier layer to be formed around the particle P inan OLED display device according to an embodiment of the presentinvention; FIG. 9(a) is a schematic view of a cross-section including adiameter of the particle P (cross-section taken along line 9A-9A′ inFIG. 9(b)), and FIG. 9(b) is a plan view as seen in the normaldirection.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an organic EL display device and a method for producing thesame according to an embodiment of the present invention will bedescribed with reference to the drawings. The embodiments of the presentinvention are not limited to the embodiments described below as anexample.

First, with reference to FIG. 1(a) and FIG. 1(b), a basic structure ofan OLED display device 100 according to an embodiment of the presentinvention will be described. FIG. 1(a) is a schematic partialcross-sectional view of an active region of the OLED display device 100according to an embodiment of the present invention. FIG. 1(b) is apartial cross-sectional view of a TFE structure 10 formed on an OLED 3.

The OLED display device 100 includes a plurality of pixels, and each ofthe pixels includes at least one organic EL element (OLED). Herein, astructure corresponding to one OLED will be described for the sake ofsimplicity.

As shown in FIG. 1(a), the OLED display device 100 includes a flexiblesubstrate (hereinafter, may be referred to simply as a “substrate”) 1, acircuit (back plane) 2 formed on the substrate 1 and including a TFT,the OLED 3 formed on the circuit 2, and the TFE structure 10 formed onthe OLED 3. The OLED 3 is, for example, of a top emission type. Anuppermost portion of the OLED 3 is, for example, an upper electrode or acap layer (refractive index adjusting layer). An optional polarizingplate 4 is located on the TFE structure 10.

The substrate 1 is, for example, a polyimide film having a thickness of15 μm. The circuit 2 including the TFE has a thickness of, for example,4 μm. The OLED 3 has a thickness of, for example, 1 μm. The TFEstructure 10 has a thickness that is, for example, less than, or equalto, 1.5 μm.

FIG. 1(b) is a partial cross-sectional view of the TFE structure 10formed on the OLED 3. The TFE structure 10 includes a first inorganicbarrier layer (e.g., SiN layer) 12, an organic barrier layer (e.g.,acrylic resin layer) 14, and a second inorganic barrier layer (e.g., SiNlayer) 16. The first inorganic barrier layer 12 is formed immediately onthe OLED 3. The organic barrier layer 14 is in contact with a topsurface of the first inorganic barrier layer 12, and includes aplurality of solid portions distributed discretely. The second inorganicbarrier layer 16 is in contact with the top surface of the firstinorganic barrier layer 12 and top surfaces of the plurality of solidportions of the organic barrier layer 14. The organic barrier layer isblack. The organic barrier layer 14 contains, for example, a dye.

Since the organic barrier layer 14 is black, it may be inspected in ashort time and/or at low cost whether or not the organic barrier layer14 is formed in a region where the organic barrier layer 14 needs to beformed. This improves the yield of the OLED display device 100. A methodfor producing the OLED display device 100 and a method for performingthe inspection will be described below.

The organic barrier layer 14 merely needs to be sufficiently coloredblack to be visually recognizable in an inspection process describedbelow, and does not need to be light-blocking.

The first inorganic barrier layer 12 and the second inorganic barrierlayer 16 are each, for example, an SiN layer (e.g., Si₃N₄ layer) havinga thickness of, for example, 400 nm. The first inorganic barrier layer12 and the second inorganic barrier layer 16 each have a thickness of200 nm or greater and 1000 nm or less independently. The thickness ofthe TFE structure 10 is preferably 400 nm or greater and less than 2 μm,and more preferably 400 nm or greater and less than 1.5 μm. Thethickness of the organic barrier layer (solid portion) 14, which dependson the size of the protruding portion of the surface of the firstinorganic barrier layer 12 or the size of the particle, may be 1 μm atthe maximum. The thickness of the organic barrier layer (solid portion)14 is typically 200 nm or greater and 500 nm or less.

The TFE structure 10 is formed so as to protect an active region (seethe active region R1 in FIG. 2) of the OLED display device 100. Asdescribed above, the TFE structure 10 includes, in at least the activeregion, the first inorganic barrier layer 12, the organic barrier layer14 and the second inorganic barrier layer 16 in this order, with thefirst inorganic barrier layer 12 being closest to the OLED 3. Theorganic barrier layer 14 is not present as a film covering the entiretyof the active region, but has openings. Portions of the organic barrierlayer 14 where an organic film is actually present, namely, portionsexcept for the openings, will be referred to as “solid portions”. The“openings” (may also referred to as “non-solid portions”) do not need tobe enclosed by the solid portions and may include a cutout portion andthe like. In the openings, the first inorganic barrier layer 12 and thesecond inorganic barrier layer 16 are in direct contact with each other.The openings of the organic barrier layer 14 include at least an openingformed so as to enclose the active region, and the active region isfully enclosed by the portion in which the first inorganic barrier layer12 and the second inorganic barrier layer 16 are in direct contact witheach other (hereinafter, such a portion will be referred to as an“inorganic barrier layer joint portion”).

With reference to FIG. 2 through FIG. 6, a structure of, and a methodfor producing, an OLED display device according to an embodiment of thepresent invention will be described.

FIG. 2 is a schematic plan view of the OLED display device 100 accordingto an embodiment of the present invention.

The OLED display device 100 includes the flexible substrate 1, thecircuit (back plane) 2 formed on the substrate 1, a plurality of theOLEDs 3 formed on the circuit 2, and the TFE structure 10 formed on theOLEDs 3. A layer including the plurality of OLEDs 3 may be referred toas an “OLED layer 3”. The circuit 2 and the OLED layer 3 may share apart of components. The optional polarizing plate (see reference numeral4 in FIG. 1) may further be located on the TFE structure 10. Inaddition, for example, a layer having a touch panel function may belocated between the TFE structure 10 and the polarizing plate. Namely,the OLED display device 100 may be altered to a display device includingan on-cell type touch panel.

The circuit 2 includes a plurality of TFTs (not shown), and a pluralityof gate bus lines (not shown) and a plurality of source bus lines (notshown) each connected with either one of the plurality of TFTs (notshown). The circuit 2 may be a known circuit that drives the pluralityof OLEDs 3. The plurality of OLEDs 3 are each connected with either oneof the plurality of TFTs included in the circuit 2. The OLEDs 3 may beknown OLEDs.

The OLED display device 100 further includes a plurality of terminals 38located in a peripheral region R2 outer to the active region R1 (regionenclosed by the dashed line in FIG. 2), where the plurality of OLEDs 3are located, and also includes a plurality of lead wires 30 connectingeach of the plurality of terminals 38 and either one of the plurality ofgate bus lines or either one of the plurality of source bus lines toeach other. The TFE structure 10 is formed on the plurality of OLEDs 3and on a portion of the plurality of lead wires 30 that is close to theactive region R1. Namely, the TFE structure 10 covers the entirety ofthe active region R1 and is also selectively formed on the portion ofthe plurality of lead wires 30 that is close to the active region R1.Neither a portion of the plurality of lead wires 30 that are closer tothe terminals 38, nor the terminals 38, is covered with the TFEstructure 10.

Hereinafter, an example in which the lead wires 30 and the terminals 38are integrally formed in the same conductive layer will be described.Alternatively, the lead wires 30 and the terminals 38 may be formed indifferent conductive layers (encompassing stack structures).

Now, with reference to FIG. 3(a) through FIG. 3(c), the TFE structure 10of the OLED display device 100 will be described. FIG. 3(a) is across-sectional view taken along line 3A-3A′ in FIG. 2. FIG. 3(b) is across-sectional view taken along line 3B-3B′ in FIG. 2. FIG. 3(c) is across-sectional view taken along line 3C-3C′ in FIG. 2.

As shown in FIG. 3(a) and FIG. 3(b), the TFE structure 10 includes thefirst inorganic barrier layer 12 formed on the OLED 3, the organicbarrier layer 14, and the second inorganic barrier layer 16 in contactwith the first inorganic barrier layer 12 and the organic barrier layer14. The first inorganic barrier layer 12 and the second inorganicbarrier layer 16 are each, for example, an SiN layer, and areselectively formed in a predetermined region so as to cover the activeregion R1 by plasma CVD by use of a mask. In general, a surface of alayer formed by a thin film deposition method (e.g., CVD, sputtering,vacuum vapor deposition) reflects a stepped portion in an underlyinglayer. The organic barrier layer (solid portion) 14 is formed onlyaround the protruding portion of the surface of the first inorganicbarrier layer 12.

FIG. 3(a) is a cross-sectional view taken along line 3A-3A′ in FIG. 2,and shows a portion including a particle P. The particle P is amicroscopic dust particle generated during the production of the OLEDdisplay device, and is, for example, a microscopic piece of brokenglass, a metal particle or an organic particle. Such a particle isespecially easily generated in the case where mask vapor deposition isused.

As shown in FIG. 3(a), the organic barrier layer (solid portion) 14includes a portion 14 b formed around the particle P. A reason for thisis that an acrylic monomer supplied after the first inorganic barrierlayer 12 is formed is condensed and present locally, namely, around asurface of a first inorganic barrier layer 12 a on the particle P (thesurface has a tapering angle larger than 90 degrees). The organicbarrier layer 14 includes the opening (non-solid portion) on a flatportion of the first inorganic barrier layer 12.

Now, with reference to FIG. 4(a) through FIG. 4(c), a structure of theportion including the particle P will be described. FIG. 4(a) is anenlarged view of the portion including the particle P shown in FIG.3(a). FIG. 4(b) is a schematic plan view showing the size relationshipamong the particle P, the first inorganic barrier layer (SiN layer) 12covering the particle P and the organic barrier layer 14. FIG. 4(c) is aschematic cross-sectional view of the first inorganic barrier layercovering the particle P.

In the case where the particle P (having a diameter that is, forexample, longer than, or equal to, 1 μm) is present, a crack (defect) 12c may be formed in the first inorganic barrier layer as shown in FIG.4(c). As described below, this is considered to be caused by impingementof the SiN layer 12 a growing from a surface of the particle P and anSiN layer 12 b growing from a flat portion of a surface of the OLED 3.In the case where such a crack 12 c is present, the level of barrierproperty of the TFE structure 10 is decreased.

In the TFE structure 10 of the OLED display device 100, as shown in FIG.4(a), the organic barrier layer 14 is formed to fill the crack 12 c ofthe first inorganic barrier layer 12, and a surface of the organicbarrier layer 14 couples a surface of the first inorganic barrier layer12 a on the particle P and a surface of the first inorganic barrierlayer 12 b on the flat portion of the OLED 3 to each other continuouslyand smoothly. The organic barrier layer 14, which is formed by curing aphotocurable resin in a liquid state as described below, has a recessedsurface by a surface tension. In this state, the photocurable resinexhibits a high level of wettability to the first inorganic barrierlayer 12. If the level of wettability of the photocurable resin to thefirst inorganic barrier layer 12 is low, the surface of the organicbarrier layer 14 may protrude. The organic barrier layer 14 may also beformed with a small thickness on the first inorganic barrier layer 12 aon the particle P.

The organic barrier layer (solid portion) 14 having the recessed surfaceconnects the surface of the first inorganic barrier layer 12 a on theparticle P and the surface of the first inorganic barrier layer 12 b onthe flat portion to each other continuously and smoothly. Therefore, thesecond inorganic barrier layer 16 formed thereon is a fine film with nodefect. As can be seen, even if the particle P is present, the organicbarrier layer 14 keeps high the level of barrier property of the TFEstructure 10.

As shown in FIG. 4(b), the organic barrier layer 14 (solid portion) isformed in a ring shape around the particle P. Where the particle P has adiameter (equivalent circle diameter) of about 1 μm as seen in adirection normal to the surface of the OLED 3, the ring-shaped solidportion has a diameter D₀ (equivalent circle diameter) that is, forexample, longer than, or equal to, 2 μm.

In this example, the organic barrier layer 14 is formed only in adiscontinuous portion in the first inorganic barrier layer 12 formed onthe particle P, and the particle P is already present before the firstinorganic barrier layer 12 is formed on the OLED 3. The particle P maybe present on the first inorganic barrier layer 12. In this case, theorganic barrier layer 14 is formed only at the border, namely, in adiscontinuous portion, between the first inorganic barrier layer 12 andthe particle P on the first inorganic barrier layer 12, and thusmaintains the barrier property of the TFE structure 10 like in theabove-described case. The organic barrier layer 14 may also be formedwith a small thickness on the surface of the first inorganic barrierlayer 12 a on the particle P, or on the surface of the particle P. Inthis specification, the expression that “the organic barrier layer ispresent around the particle P” encompasses all these forms.

The organic barrier layer (solid portion) 14 is not limited to beingformed as in the example of FIG. 3(a), and may be formed only around theprotruding portion of the surface of the first inorganic barrier layer12 for substantially the same reason. Examples of the other regionswhere the organic barrier layer (solid portion) 14 may be formed will bedescribed below.

Now, with reference to FIG. 3(b), a structure of the TFE structure 10 onthe lead wires 30 will be described. FIG. 3(b) is a cross-sectional viewtaken along line 3B-3B′ in FIG. 2; more specifically, is across-sectional view of portions 32, of the lead wires 30, close to theactive region R1.

As shown in FIG. 3(b), the organic barrier layer (solid portions) 14includes portions 14 c formed around the protruding portions of thesurface of the first inorganic barrier layer 12. The protruding portionsreflect the cross-sectional shape of the portions 32 of the lead wires30.

The lead wires 30 are patterned by the same step as that of, forexample, the gate bus lines or the source bus lines. Thus, in thisexample, the gate bus lines and the source bus lines formed in theactive region R1 also have the same cross-sectional structure as that ofthe portion 32, of each of the lead wires 30, close to the active regionR1 shown in FIG. 3(b). It should be noted that typically, a flatteninglayer is formed on the gate bus lines and the source bus lines formed inthe active region R1, and thus no stepped portion is formed at thesurface of the first inorganic barrier layer 12 on the gate bus linesand the source bus lines.

The portion 32 of the lead wire 30 may have, for example, a forwardtapering side surface portion (inclining side surface portion) having atapering angle smaller than 90 degrees. In the case where the lead wire30 includes the forward tapering side surface portion, formation ofdefects in the first inorganic barrier layer 12 and the second inorganicbarrier layer 16 formed on the lead wire 30 is prevented. Namely, themoisture-resistance reliability of the TFE structure 10 is improved. Thetapering angle of the forward tapering side surface portion ispreferably smaller than, or equal to, 70 degrees.

The active region R1 of the OLED display device 100 is substantiallycovered with the inorganic barrier layer joint portion, in which thefirst inorganic barrier layer 12 and the second inorganic barrier layer16 are in direct contact with each other, except for the regions wherethe organic barrier layer 14 is selectively formed. Therefore, it doesnot occur that the organic barrier layer 14 acts as a moisture entranceroute to allow the moisture to reach the active region R1 of the OLEDdisplay device.

The OLED display device 100 according to an embodiment of the presentinvention is preferably usable for, for example, medium- to small-sizedhigh-definition smartphones and tablet terminals. In a medium- tosmall-sized (e.g., 5.7-inch) high-definition (e.g., 500 ppi) OLEDdisplay device, it is preferred that lines (encompassing the gate buslines and the source bus lines) in the active region R1 have across-sectional shape, taken in a direction parallel to a line widthdirection, close to a rectangle (side surfaces of the lines have atapering angle of about 90 degrees) in order to allow the lines to havea sufficiently low resistance with a limited line width. In order toform the lines having a low resistance, the tapering angle of theforward tapering side surface portion TSF may be larger than 70 degreesand smaller than 90 degrees, or the tapering angle may be about 90degrees in the entire length of the lines with no forward tapering sidesurface portion TSF being provided.

Now, FIG. 3(c) will be referred to. FIG. 3(c) is a cross-sectional viewof a region where the TFE structure 10 is not formed. In this region, aterminal portion 38 has the same cross-sectional structure as that ofportions 36 of the lead wires 30 shown in FIG. 3(c). The portions 36 ofthe lead wires 30 shown in FIG. 3(c) may have a tapering angle of, forexample, about 90 degrees.

Now, with reference to FIG. 5 and FIG. 6, the organic barrier layer 14formed around a bank structure BS will be described. The organic barrierlayer (solid portion) 14 is also formed around a protruding portion ofthe surface of a portion, of the first inorganic barrier layer 12, thatis used to form the bank structure BS. FIG. 5 is a plan viewschematically showing the plurality of pixels and a bank layer 48included in the OLED display device 100. FIG. 6(a) and FIG. 6(b) areeach a schematic cross-sectional view of the OLED display device 100.FIG. 6(a) is a cross-sectional view taken along line 6A-6A′ in FIG. 5,and FIG. 6(b) is a cross-sectional view taken along line 6B-6B′ in FIG.5.

As shown in FIG. 5 and FIG. 6(a), the OLED display device 100 furtherincludes the bank layer 48 defining each of the plurality of pixels. Thebank layer 48 has an inclining surface enclosing each of the pluralityof pixels. The plurality of solid portions of the organic barrier layer14 each include a pixel periphery solid portion 14 a extending on thefirst inorganic barrier layer 12 from an inclining surface S12 to aperipheral area in the pixel.

As shown in FIG. 6(a), the bank structure BS includes the bank layer 48formed of an insulating material (the bank layer may be referred to alsoas a “PDL (Pixel Defining Layer)”). The bank layer 48 is formed betweena lower electrode 42 and an organic layer 44 of the OLED 3. As shown inFIG. 6(a), the OLED 3 includes the lower electrode 42, the organic layer44 formed on the lower electrode 42, and an upper electrode 46 formed onthe organic layer 44. In this example, the lower electrode 42 and theupper electrode 46 respectively act as an anode and a cathode of theOLED 3. The upper electrode 46 is a common electrode formed for theentirety of the pixels in the active region. By contrast, the lowerelectrode (pixel electrode) 42 is formed for each of the pixels. In thestructure in which the bank layer 48 is present between the lowerelectrode 42 and the organic layer 44, no holes are injected from thelower electrode 42 into the organic layer 44. Therefore, the regionwhere the bank layer 48 is present does not act as a pixel Pix. Thus,the bank layer 48 defines an outer perimeter of the pixel Pix.

As shown in FIG. 5, each pixel Pix is defined by an opening in the banklayer 48. The bank layer 48 is formed to be, for example,lattice-shaped. A side surface of the opening of the bank layer 48 hasan inclining surface including the forward tapering side surface portionTSF. The inclining surface of the bank layer 48 encloses each pixel. Thebank layer 48 is formed of, for example, a photosensitive resin (e.g.,polyimide or acrylic resin). The bank layer 48 has a thickness of, forexample, 1 μm to 2 μm. The inclining surface of the bank layer 48 isinclined at an inclination angle θb that is, for example, smaller than,or equal to, 60 degrees. If the inclination angle θb of the incliningsurface of the bank layer 48 is larger than 60 degrees, a defect may becaused in layers located on the bank layer 48. The layers located on thebank layer 48 (including, for example, the organic layer 44, the upperelectrode 46, the first inorganic barrier layer 12 and the secondinorganic barrier layer 16) may be included in the bank structure BS.The layers included in the bank structure BS may each have an incliningsurface enclosing each of the plurality of pixels. In the case whereeach of the layers formed on the bank layer 48 is thinner than the banklayer 48, the inclination angle of the inclining surface of the bankstructure BS is considered to be substantially equal to the inclinationangle of the inclining surface of the bank layer 48. The first inorganicbarrier layer 12 is included in the bank structure BS, and has theinclining surface S12 enclosing each of the plurality of pixels. Theorganic barrier layer (solid portion) 14 includes the pixel peripherysolid portion 14 a extending on the first inorganic barrier layer 12from the inclining surface S12 to a peripheral area in the pixel.

As shown in, for example, FIG. 6(a), in a central area of the pixel, theorganic barrier layer 14 is formed only in a discontinuous portionformed in the first inorganic barrier layer 12 by the particle P.Namely, as shown in FIG. 6(b), the organic barrier layer 14 is notpresent in a central area, of the pixel, where no particle P is present.The OLED display device with no particle P does not include the organicbarrier layer in the central area of the pixel. A particle P having asize (equivalent spherical diameter) of approximately 0.3 μm or longerand 5 μm or shorter declines the moisture-resistance reliability of theTFE structure 10. It should be noted that a particle P having a size of0.2 μm or longer and shorter than 0.3 μm may also decline themoisture-resistance reliability. A particle P having a size shorter than0.2 μm is considered to have substantially no possibility of decliningthe moisture-resistance reliability. A particle having a size longerthan 5 μm is removed by cleaning or the like.

A board of G4.5 (730 mm×920 mm) may have, for example, several tens toabout 100 particles each having a size of approximately 0.3 μm or longerand 5 μm or shorter. One OLED display device (active region) may haveapproximately several particles. Needless to say, there are OLED displaydevices with no particle P. The organic barrier layer 14 is formed of,for example, a cured photocurable resin. A portion where thephotocurable resin is actually present is referred to as a “solidportion”. As described above, the organic barrier layer 14 (solidportion) is selectively formed only around a protruding portion of thesurface of the first inorganic barrier layer 12.

As shown in, for example, FIG. 6(a), in the case where there is aparticle P in the central area of the pixel, the organic barrier layer14 is formed in a discontinuous portion formed by the particle P. Asdescribed above with reference to FIG. 4(b), the organic barrier layer(solid portion) 14 is formed in a ring shape around the particle P.Where the particle P has a diameter (equivalent circle diameter) of, forexample, about 1 μm as seen in a direction normal to the surface of theOLED 3, the ring-shaped solid portion has a diameter D₀ (equivalentcircle diameter) that is, for example, longer than, or equal to, 2 μm.In the case of, for example, a 5.7-inch display device having 2560×1440pixels (about 500 ppi), the pixel pitch is 49 μm. The size of theparticle P and the size of the organic barrier layer (solid portion) 14formed around the particle P are sufficiently smaller than the pixelpitch. Therefore, a change in the transmittance caused by the barrierlayer 14 (solid portion) formed around the particle P does not have asignificant influence on the display.

Now, with reference to FIG. 6(a) and FIG. 6(b), a further advantageprovided by the black organic barrier layer 14 included in the OLEDdisplay device 100 will be described.

Patent Document No. 3 discloses a thin film encapsulation structureincluding an organic barrier layer (may be referred to as a “flatteninglayer”; for example, an acrylic resin layer) formed selectively aroundan inclining surface of a bank structure. Patent Document No. 3 does notdisclose a colored organic barrier layer. According to the studies madeby the present inventors, unless the colored organic barrier layer isformed, the luminous intensity distribution (viewing angle dependence)of light output from the pixel may be changed by the formation of theorganic barrier layer (solid portion) around the inclining surface ofthe bank structure. When the size, shape or the like of the organicbarrier layer is different, the intensity or the luminous intensitydistribution of the light output from a periphery of the pixel isdifferent. As a result, a problem that the luminous intensitydistribution of light is different among the pixels is caused.

By contrast, as shown in FIG. 6(a) and FIG. 6(b), the OLED displaydevice 100 according to an embodiment of the present invention includesthe organic barrier layer (solid portion) 14 colored black and extendingfrom the inclining surface of the bank structure BS to a peripheral areain the pixel. Therefore, the light output from the periphery of thepixel is decreased. This uniformizes the luminous intensitydistributions of the light output from the pixels. As shown in FIG.6(a), the OLED display device 100 also includes the organic barrierlayer (solid portion) 14 around the particle P. Therefore, the light issuppressed from leaking from the vicinity of the particle P.

The organic barrier layer 14 merely needs to effectively absorb lightoutput in an oblique direction (e.g., absorb 70% or greater of thelight) in order to provide the above-described effect. The organicbarrier layer 14 may be formed of, for example, a black resist usablefor a black matrix of a color filter layer of a known display device.However, the organic barrier layer 14 does not necessarily need to havea level of light-blocking property required of a black matrix (e.g., ODvalue of about 3 to 4/μm).

Now, a method for producing an OLED display device according to anembodiment of the present invention will be described.

A step of forming the TFE structure 10 in the OLED display deviceaccording to an embodiment of the present invention includes thefollowing steps.

Step A: step of preparing an element substrate having the firstinorganic barrier layer 12 formed thereon

Step B: step of forming a liquid film containing a photosensitive resinon the first inorganic barrier layer 12

Step C: step of irradiating the liquid film with light to form a resinlayer

Step D: step of forming the organic barrier layer 14, including a stepof partially removing the resin layer by a dry process

Step D is optional and may be omitted. For example, as described below,mask exposure may be performed at the time of curing the photocurableresin to form the organic barrier layer 14.

As an example, a method for forming the organic barrier layer 14 by useof the method described in Patent Document No. 1 or 2 will be described.Regarding the method for forming the organic barrier layer, thedisclosures of Patent Documents Nos. 1 and 2 are incorporated herein byreference.

Step B includes a step of, after step A, putting the element substrateinto a chamber and supplying a vapor-like or mist-like photocurableresin (e.g., acrylic monomer) into the chamber, and a step of condensingthe photocurable resin on the first inorganic barrier layer 12 to formthe liquid film. Namely, a vapor-like or mist-like organic material issupplied onto the element substrate maintained at a temperature lowerthan, or equal to, room temperature in the chamber, and is condensed onthe element substrate. Thus, the organic material put into a liquidstate is located locally, more specifically, at the border between theside surface of the protruding portion and the flat portion of thesurface of the first inorganic barrier layer 12 by a capillary action ora surface tension of the organic material.

In the case where step B is performed by the method described in PatentDocument No. 1 or 2, the liquid film formed in step B contains, forexample, a photocurable resin (e.g., ultraviolet-curable resin) and ablack dye. The black dye may be a known dye. The black dye may contain aphotopolymerizable dye monomer. The black dye is generally a mixture ofa plurality of dyes (compounds) of different colors.

Next, step C is performed. More specifically, the organic material isirradiated with, for example, ultraviolet rays to form the photocurableresin layer (e.g., acrylic resin layer). The photocurable resin layerformed in this step typically includes a plurality of solid portionsdistributed discretely. Substantially no solid portion is present on theflat portion of the surface of the first inorganic barrier layer 12.Even if the organic material is present on the flat portion of thesurface of the first inorganic barrier layer 12, the amount (e.g.,thickness) thereof is smaller than the amount around the protrudingportion of the surface of the first inorganic barrier layer 12.Therefore, the resin layer, once formed, may be asked in, for example, asubsequent step (step D) to remove the organic material from the flatportion of the surface of the first inorganic barrier layer 12. As aresult, the organic barrier layer (solid portion) 14 is formed locally,more specifically, only around the protruding portion of the surface ofthe first inorganic barrier layer 12. In order to form the organicbarrier layer 14 in this manner, the thickness of the liquid film to beformed and/or the asking conditions (including time) may beappropriately adjusted when necessary, in addition to the above.

Alternatively, selective exposure such as mask exposure or the like maybe performed at the time of curing the photocurable resin. For example,mask exposure may be performed, so that the inorganic barrier layerjoint portion, where the first inorganic barrier layer 12 and the secondinorganic barrier layer 16 are in direct contact with each other, isformed. An opening of the organic barrier layer 14 is formed in a regioncorresponding to a light-blocking portion of the photomask. Therefore,for example, the photocurable resin layer may be exposed via a photomaskincluding a light-blocking portion formed so as to enclose the activeregion, so that the organic barrier layer 14 having an opening formed soas to enclose the active region is provided.

Then, step D is performed when necessary to form the organic barrierlayer (solid portion) 14 located locally, more specifically, only aroundthe protruding portion of the surface of the first inorganic barrierlayer 12. Step D includes a step of partially removing the photocurableresin layer by a dry process. For example, a relatively thick portion ofthe photocurable resin layer is left without being fully removed. Theexpression “remove an organic material by a dry process” indicatesremoving an organic material from the surface by ashing or by a dryprocess other than ashing (e.g., by sputtering). The expression “removean organic material by a dry process” encompasses removing the organicmaterial entirely and removing the organic material partially (e.g.,from the surface to a certain depth). The “dry process” refers to aprocess that is not a wet process using a liquid such as a releaseliquid, a solvent or the like.

Patent Document No. 1 or 2 does not disclose or suggest a step ofpartially removing a photocurable resin layer by a dry process. Thisstep enlarges a margin for the formation of the organic barrier layer.Namely, an organic barrier layer (photocurable resin layer) is onceformed in a region larger (wider) than the region where the organicbarrier layer needs to be formed, and the resultant organic barrierlayer is partially removed. In this manner, the organic barrier layer isformed only in the region where the organic barrier layer needs to beformed. This improves the yield.

Ashing oxidizes and thus removes an organic material. Ashing is usedalso to remove an organic material attached to a surface of an inorganicfilm. Ashing is used to remove the organic material entirely and also toremove the organic material partially (e.g., from a surface to a certaindepth). Ashing may be performed in, for example, an atmospherecontaining at least one of N₂O, O₂ and O₃. Ashing is roughly classifiedinto plasma ashing (or corona discharge) using plasma generated bytreating any one of the above-described types of atmospheric gas at ahigh frequency, and photo-excited ashing of irradiating atmospheric gaswith light such as ultraviolet rays or the like. Ashing may be performedby use of, for example, a known plasma ashing device, a known ashingdevice using corona discharge, a known photo-excited ashing device, aknown UV ozone ashing device or the like. In the case where an SiN filmis formed by CVD as each of the first inorganic barrier layer 12 and thesecond inorganic barrier layer 16, N₂O is used as material gas.Therefore, use of N₂O for ashing provides an advantage of simplifyingthe ashing device.

Ashing results in shaving the surface the organic barrier layer 14substantially uniformly, and also oxidizing the surface the organicbarrier layer 14 to modify the surface of the organic barrier layer 14to be hydrophilic. Ashing also results in forming extremely tinyconcaved and convexed portions to increase the surface area size of theorganic barrier layer 14. The effect of ashing of increasing the surfacearea size is greater for the surface of the organic barrier layer 14than for the first inorganic barrier layer 12 formed of an inorganicmaterial. Since the surface of the organic barrier layer 14 is modifiedto be hydrophilic and the surface area size thereof is increased, theadhesiveness between the organic barrier layer 14 and the secondinorganic barrier layer 16 is improved.

In order to improve the adhesiveness between the first inorganic barrierlayer 12 and the organic barrier layer 14, the surface of the firstinorganic barrier layer 12 may be exposed to plasma ashing (e.g., plasmaprocess and/or corona process) or to photo-excited ashing before theorganic barrier layer 14 is formed. Namely, the step of forming the TFEstructure 10 may further include a step of, after step A and before stepB, performing plasma ashing (e.g., plasma process and/or corona process)or photo-excited ashing. Such a step provides an advantage that the sidesurface of the protruding portion of the surface of the first inorganicbarrier layer 12 is modified to be lyophilic to the liquid film formedin step B, or that the degree of the lyophilic property of the sidesurface is improved. Alternatively, the surface of the flat portion ofthe first inorganic barrier layer 12 may be modified to be repellingagainst the liquid film formed in step B. For example, the incliningsurface S12 of the first inorganic barrier layer 12 of the bankstructure BS (see FIG. 6(a) and FIG. 6(b)) may be lyophilic to theliquid film formed in step B, whereas the region enclosed by the bankstructure BS may be repelling against the liquid film formed in step B.

The above-described modification of the surface may also be realized by,for example, a silane coupling agent (hydrophilic or hydrophobic).Namely, the step of forming the TFE structure 10 may further include astep of, after step A and before step B, supplying a silane couplingagent onto the surface of the first inorganic barrier layer 12. Eitherthe step of supplying the silane coupling agent or the step of askingmay be performed. Alternatively, after the surface of the firstinorganic barrier layer 12 is asked, the silane coupling agent may besupplied. Supply of the silane coupling agent may modify the surface ofthe first inorganic barrier layer 12 to be hydrophilic or hydrophobic.

Still alternatively, for example, a photolithography process may be usedto modify a particular region of the surface to be hydrophilic orhydrophobic by use of a silane coupling agent. For example, theinclining surface S12 of the first inorganic barrier layer 12 of thebank structure BS may be modified to be lyophilic to the liquid film,whereas the region enclosed by the bank structure BS may be modified tobe repelling against the liquid film.

Step D may further include a step of performing plasma ashing (e.g.,plasma process and/or corona process) or photo-excited ashing. This stepremoves the organic material from the surface of the flat portion of thefirst inorganic barrier layer 12 more certainly.

As described above, the active region of the OLED display device 100according to an embodiment of the present invention is fully enclosed bythe inorganic barrier layer joint portion, where the first inorganicbarrier layer 12 and the second inorganic barrier layer 16 are in directcontact with each other. With such a structure, the OLED display device100 has a higher level of moisture-resistance reliability than an OLEDdisplay device including an organic barrier layer formed by the methoddescribed in Patent Document No. 1 or 2.

According to the studies made by the present inventors, in the casewhere the organic barrier layer is formed by the method described inPatent Document No. 1 or 2, there may be a problem that a sufficientlyhigh level of moisture-resistance reliability is not provided. Thisproblem has been found to be caused by water vapor in the air reachingthe active region (may also be referred to as an “element formationregion” or a “display region”) on the element substrate via the organicbarrier layer.

In the case where an organic barrier layer is formed by printing such asinkjet printing or the like, the organic barrier layer may be adjustedto be formed only in the active region (may also be referred to as an“element formation region” or a “display region”) on the elementsubstrate but not in a region other than the active region. Therefore,there is a region where the first inorganic barrier layer and the secondinorganic barrier layer are in direct contact with each other around theactive region (outer to the active region). The organic barrier layer isfully enclosed by the first inorganic barrier layer and the secondinorganic barrier layer and is isolated from the outside of the firstinorganic material layer and the second inorganic material layer.

By contrast, with the method for forming the organic barrier layerdescribed in Patent Document 1 or 2, a resin (organic material) issupplied onto the entire surface of the element substrate, and thesurface tension of the resin in a liquid state is used to locate theresin locally, more specifically, at the border between the surface ofthe substrate and the side surface of the protruding portion on thesurface of the element substrate. Therefore, the organic barrier layermay also be formed in a region other than the active region (the regionother than the active region may also be referred to as a “peripheralregion”), namely, in a terminal region, where the plurality of terminalsare located, and in a lead wire region, where the lead wires extendingfrom the active region to the terminal region are formed. Specifically,the resin is present locally, more specifically, at, for example, theborder between the side surfaces of the lead wires and the terminals andthe surface of the substrate. In this case, an end of the organicbarrier layer formed along the lead wires is not enclosed by the firstinorganic barrier layer or the second inorganic barrier layer, but isexposed to the air (ambient atmosphere). The organic barrier layer islower in the barrier property against water vapor than the inorganicmaterial layers (inorganic barrier layers). Therefore, the organicbarrier layer formed along the lead wires acts as a route that leads thewater vapor in the air to the active region.

With the production method according to an embodiment of the presentinvention, as described above, the openings of the organic barrier layer14 include an opening formed so as to enclose at least the activeregion, and the active region is fully enclosed by the inorganic barrierlayer joint portion, where the first inorganic barrier layer 12 and thesecond inorganic barrier layer 16 are in direct contact with each other.Therefore, the organic barrier layer does not act as a route that leadsthe water vapor in the air to the active region.

The organic barrier layer 14 of the OLED display device 100 according toan embodiment of the present invention is not limited to being formed bythe above-described method, and may be formed by, for example, spraying,spin-coating, slit-coating, screen printing or inkjet printing. Namely,step B may be performed by spraying, spin-coating, slit-coating, screenprinting or inkjet printing. In the case where such a method is used, aphotosensitive resin (positive or negative) may be used as well as aphotocurable resin (negative). In the case where a positivephotosensitive resin is used, a photomask having an openingcorresponding to a region where the inorganic barrier layer jointportion is to be formed is used.

In the case where any of such methods is used, the liquid film (amaterial containing a photosensitive resin used to form the liquid filmmay be referred to as a “coating liquid”) is not limited to a dye andmay contain a pigment. A known black pigment, for example, carbon black,may be used. Usable as a photosensitive resin (e.g., photocurable resin)having black pigment dispersed therein is, for example, a black resistusable for a black matrix of a color filter layer of a liquid crystaldisplay device. The organic barrier layer merely needs to besufficiently colored black to be visually recognizable in an inspectionprocess described below, and does not necessarily need to have alight-blocking property require of a black matrix (e.g., OD value ofabout 3 to 4/μm). As described above, the thickness of the organicbarrier layer 14 is less than, or equal to, 1 μm, typically, 200 nm orgreater and 500 nm or less. Therefore, even a usual photosensitiveresist for a black matrix may be sufficiently exposed to light (e.g.,cured) with an exposure amount of, for example, 150 mJ/cm² or less. Asthe black pigment, a mixture of a plurality of pigments of differentcolors may be used.

In the case where the organic barrier layer 14 is formed by inkjetprinting, the organic barrier layer (solid portion) may be selectivelyformed only in a particular region. Therefore, the inorganic barrierlayer joint portion is formed with no mask exposure. Even with printingsuch as screen printing, inkjet printing or the like, the resultantorganic barrier layer 14 is thinner than a relatively thick organicbarrier layer having a thickness of about 5 μm to about 20 μm, which isused for a thin film encapsulation structure of an OLED display devicecurrently commercially available. In this case, the photosensitive resinto be used is photo-curable (i.e., negative).

In the case where the organic barrier layer is formed by inkjetprinting, a region to which the coating liquid is to be supplied needsto be specified. Therefore, the method for producing the OLED displaydevice in an embodiment includes a foreign object detection step and aninkjet printing step.

FIG. 7 is a schematic view showing a foreign object detection device 50usable for the method for producing an OLED display device according toan embodiment of the present invention. FIG. 8 is a schematic viewshowing an inkjet device 60 usable for the method for producing an OLEDdisplay device according to an embodiment of the present invention.

The foreign object detection device 50 shown in FIG. 7 includes acontroller 52 and a detection head 54. The controller 52 controls anoperation of the detection head 54 and also controls an operation of astage 70. The stage 70 is capable of receiving a substrate 100M andtransporting the substrate 100M in an x-axis direction and a y-axisdirection. The stage 70 is capable of, for example, attracting andsecuring the substrate 100M, and/or transporting the substrate 100M in afloating state (contactless transportation). The substrate 100M is anelement substrate formed by use of a G4.5 mother board, and includes thecomponents up to the first inorganic barrier layer.

The controller 52 includes a memory and a processor (neither is shown),and controls the operation of the detection head 54 and/or the stage 70in accordance with information stored on the memory, such that thedetection head scans on the substrate 100M. A signal to control thedetection head 54 and/or the stage 70 to operate is generated by theprocessor and supplied to the detection head 54 and/or the stage 70 viaan interface (represented by the arrow in the figure).

The detection head 54 includes, for example, a laser light source (e.g.,semiconductor laser element), an image-forming optical system, and animage-capturing element (none of these components is shown). Laser lightis directed toward a predetermined position on the substrate 100M, andthe light scattered by the substrate 100M is caused, by theimage-forming optical system, to form an image on a light receivingsurface of the image-capturing element. Regarding the result ofimage-capturing performed by the image-capturing element, the processorfinds whether or not there is a particle, the size of the particle, andthe like in accordance with a predetermined algorithm, and stores theobtained results on the memory. Such a foreign object inspection deviceis described in, for example, Japanese Laid-Open Patent Publication No.2016-105052. The entirety of the disclosure of Japanese Laid-Open PatentPublication No. 2016-105052 is incorporated herein by reference. As theforeign object inspection device 50, for example, HS-930 produced byToray Engineering Co., Ltd. is preferably usable. HS-930 is capable ofdetecting a foreign object having a size of 0.3 μm (evaluation performedby scattering standard particles). HS-930 is capable of inspecting aG4.5 board in a time period shorter than 60 seconds.

The standard particles are true sphere polystyrene latex particles. Theactual particle P is a microscopic piece of broken glass, a metalparticle or an organic particle (organic EL material), and is coveredwith an SiN layer (refractive index: about 1.8; second inorganic barrierlayer). Therefore, the actual particle P is more easily detectable thanthe standard particle. With the above-described foreign objectinspection device using scattered laser light, a foreign object havingan equivalent spherical diameter of 0.2 μm or longer is detected.

The inkjet device 60 shown in FIG. 8 includes a controller 62, an inkjethead 64, and a UV (ultraviolet) irradiation head 66.

The controller 62 includes a memory and a processor (neither is shown),and controls the operation of the inkjet head 64, the irradiation head66 and/or the stage 70 in accordance with information stored on thememory, such that the inkjet head 64 and the UV irradiation head 66 moveto a desired position on the substrate 100M.

A signal to control the inkjet head 64, the UV irradiation head 66and/or the stage 70 to operate is generated by the processor andsupplied to the inkjet head 64, the UV irradiation head 66 and/or thestage 70 via interfaces (represented by the arrows in the figure). Forexample, position information (e.g., xy coordinates), on the position atwhich the particle is present, stored on the memory of the controller 52of the foreign object detection device 50 is received by the controller62. Based on the position information, microscopic liquid drops of thecoating liquid containing the photocurable resin are supplied from theinkjet head 64. The amount of the coating liquid (the number of themicroscopic liquid drops, namely, the number of shots) supplied from theinkjet head 64 is, for example, found by the processor based on sizeinformation on the particle stored on the memory of the controller 52 ofthe foreign object detection device 50 and received by the controller62.

Then, the UV irradiation head 66 directs ultraviolet rays to, and thuscures, the supplied photocurable resin to form the organic barrierlayer. This operation is performed on each of the particles.

FIG. 8 shows the inkjet head 64 and the UV irradiation head 66 as beingseparate from each other. Alternatively, the inkjet head 64 and the UVirradiation head 66 may be provided as one head. An LED or asemiconductor laser element may be used as an ultraviolet source, sothat the UV irradiation device 66 is realized as a compact deviceincluding a light source itself. Alternatively, the UV irradiationdevice 66 may include only an output end of an optical fiber and a lensunit provided when necessary. In this case, as an ultraviolet sourcethat emits ultraviolet rays toward an input end of the optical fiber, anLED, a semiconductor laser or any of various other ultraviolet sources(e.g., lamp sources such as, for example, a mercury xenon lamp, asuper-high pressure mercury lamp and the like) is usable. Inconsideration of the combining efficiency, it is preferred to use alight source capable of oscillating laser light, for example, an LED, asemiconductor laser element or the like. In the case where the UVirradiation head 66 and an ultraviolet source are located separatelyfrom each other, there is an advantage that in a series of stepsincluding the detection of a foreign object, the supply of a coatingliquid and the irradiation with ultraviolet rays, the influence exertedby heat generation caused by the light source on the OLED 3 in thesubstrate 100M is decreased.

Alternatively, for example, a plurality of inkjet heads may be prepared.For example, two or more inkjet heads generating different sizes ofmicroscopic liquid drops may be prepared, so that different inkjet headsare used for particles of different sizes.

For example, the inkjet head 64 preferably usable may generatemicroscopic liquid drops each having a volume of the order of 1 fL (1 fLor larger and smaller than 10 fL) or may generate microscopic liquiddrops each having a volume smaller than 1 fL. 1 fL corresponds to avolume of a sphere having a diameter of about 1.2 μm, and 0.1 fLcorresponds to a volume of a sphere having a diameter of about 0.6 μm.For example, the inkjet device (Super Inkjet (registered trademark))produced by SIJ Technology Inc., capable of injecting 0.1 fL microscopicliquid drops, is preferably usable.

Now, with reference to FIG. 9(a) and FIG. 9(b), the volume of theorganic barrier layer (solid portion) to be formed around the particle Pand a preferred size of the microscopic liquid drops used to form theorganic barrier layer will be described. FIG. 9(a) and FIG. 9(b) areschematic views provided to describe a preferred range of the volume ofthe organic barrier layer to be formed around the particle P in the OLEDdisplay device according to an embodiment of the present invention. FIG.9(a) is a cross-sectional view taken along line 9A-9A′ in FIG. 9(b), andis a schematic view of a cross-section including a diameter of theparticle P. FIG. 9(b) is a plan view as seen in a direction normal tothe surface of the OLED.

Now, it is assumed that the particle P or the first inorganic barrierlayer 12 a formed to cover the particle P (the particle P and the firstinorganic barrier layer 12 a formed to cover the particle P may becollectively referred to as a “protruding portion by the particle P”) isspherical. An organic barrier layer 14 v around the particle P may beformed to cover the particle P and/or the inorganic barrier layer 12 aon the particle P. However, if the organic barrier layer 14 v is toothick, the protruding portion by the particle P may be visuallyrecognized by a refraction function (lens effect) of the organic barrierlayer 14 v. Therefore, it is preferred that as shown in FIG. 9(a), theorganic barrier layer 14 v is formed only in a region of a radius R ofthe protruding portion by the particle P, namely, from the bottom to thecenter of the protruding portion. The organic barrier layer 14 vprovided in this manner may be formed by adjusting the volume of thecoating liquid to be supplied (in the case where the coating liquidcontains a solvent, the volume of the solid content) and/or by adjustingthe asking conditions (e.g., time). Ashing will be described below.

Assuming that a recessed surface of the organic barrier layer 14 v is acurved surface having a radius of curvature that is the same as theradius R of the protruding portion by the particle P, the volume V₀ ofthe organic barrier layer 14 v shown in FIG. 9(a) and FIG. 9(b) isrepresented by the following expression (1).V ₀=(4−π)πR ³  (1)

When the radius R of the protruding portion by the particle P is 0.15μm, V₀ is about 0.009 fL. When the radius R is 0.25 μm, V₀ is about 0.04fL. When the radius R is 2.5 μm, V₀ is about 42 fL.

It is preferred that the volume of the organic barrier layer 14 v islarger than, or equal to, about a half of V₀. If the volume of theorganic barrier layer 14 v is smaller than this range, the formation ofthe organic barrier layer 14 v may prevent formation of the secondinorganic barrier layer 16 with a fine film with no defect. The upperlimit of the volume of the organic barrier layer 14 v may be a level atwhich the protruding portion by the particle P is not visuallyrecognized by the refraction function (lens effect). The upper limitpreferably does not exceed five times of V₀, and preferably does notexceed twice of V₀. In the case where the radius R of the protrudingportion by the particle P is shorter than 2.5 μm (in the case where V₀is smaller than about 42 fL), the volume of the organic barrier layer 14v is not limited to the above-described range. The volume of the organicbarrier layer 14 v is merely required not to exceed about 200 fL, and ispreferably smaller than, or equal to, about 100 fL.

It is preferred that the size of the microscopic liquid drops isappropriately set in accordance with the radius R of the protrudingportion by the particle P. It is preferred that, for example, the sizeof the microscopic liquid drops is set such that one to three dropssatisfy V₀. A solvent may be incorporated into the coating liquid, sothat the microscopic liquid drops are made large with respect to thesolid content in the coating liquid (amount left as the organic barrierlayer 14 v in a final state) (the size of the microscopic liquid dropsmay be increased to, for example, a range from a size exceeding 1 timethe original size to a size 10 times the original size).

A protruding portion, by the particle P, having a diameter shorter than0.2 μm (having a radius R shorter than 0.1 μm) is considered to havesubstantially no influence on the moisture-resistance reliability evenif the organic barrier layer 14 v is not provided. Therefore, it ismerely needed to detect protruding portions, by the particle P, having adiameter of 0.2 μm or longer (having a radius R of 0.1 μm or longer) andform the organic barrier layer 14 v in corresponding portions.

It is not efficient to supply a microscopic liquid drop of 0.1 fL agreat number of times for a particle P having a diameter of 5 μm (havinga radius R of 2.5 μm). Therefore, for example, an inkjet head generatingmicroscopic liquid drops smaller than 1 fL (e.g., 0.1 fL) and an inkjethead generating microscopic liquid drops of 10 fL or larger and smallerthan 0.5 pL (e.g., 50 fL) may be prepared, so that one of the injectheads is selected in accordance with the size of the particle P. The UVirradiation head 66 is commonly usable. Needless to say, three or moreinkjet heads generating microscopic liquid drops of different sizes maybe prepared.

As described above, the portion 14 b of the organic barrier layer 14 maybe formed around the particle P. By contrast, the pixel periphery solidportion 14 a, of the organic barrier layer 14, extending on the firstinorganic barrier layer 12 from the inclining surface S12 to aperipheral area in the pixel, is more efficiently formed by use of aninkjet head that generates microscopic liquid drops of 10 fL or largerand smaller than 100 pL (e.g., 200 fL). The position of the pixelperiphery solid portion 14 a is determined in advance. Therefore, aninkjet device may be separately prepared, and the pixel periphery solidportion 14 a may be formed in accordance with the design data.

A coating liquid containing a photocurable resin (monomer) contains aphotoinitiator (radical polymerization initiator or cationicpolymerization initiator) and also a small amount of additive such as asurfactant or the like. The photocurable resin is contained in thecoating liquid at a content of about 80% by mass to about 90% by mass,and the photoinitiator is contained at a content of about 5% by mass toabout 10% by mass. A pigment or a dye may be incorporated into thecoating liquid. In the case of a pigment is incorporated, a dispersantmay also be incorporated. A preferred viscosity is, for example, about0.5 mPa or higher and 10 Pa·s. In the case where a dye or a pigment isincorporated, it is easily checked whether or not the organic barrierlayer (solid portion) has been formed at a desired position. The pigmentneeds to be put into microscopic pieces, which raises the viscosity.Therefore, it is preferred to use a dye. In the case where, for example,microscopic liquid drops of 0.1 fL are to be generated, it is preferredthat the coating liquid does not contain a pigment or a dye. In order toadjust the viscosity or the size (volume) of the microscopic liquiddrops, a solvent (e.g., an organic solvent such as alcohol or the like)may be incorporated.

Usable as the photocurable resin may be a radical polymerizable monomercontaining a vinyl group such as an acrylic resin (acrylate monomer), ora cationic polymerizable monomer containing an epoxy group. Anappropriate photoinitiator is selected in accordance with the type ofthe resin to be used and the wavelength range of the UV light to bedirected. Instead of using the UV irradiation head 66, an ultravioletirradiation device such as a high pressure mercury lamp, a super-highpressure mercury lamp or the like may be used to, for example, irradiatethe entirety of the photocurable resin on the substrate 100M withultraviolet rays at the same time. The amount of the ultraviolet rays tobe directed (exposure amount), which depends on the thickness of theorganic barrier layer 14 to be formed, is, for example, 50 mJ/cm² orlarger and 200 mJ/cm² or smaller, preferably 100 mJ/cm² or larger and150 mJ/cm² or smaller, with i line of 365 nm.

The production method described above includes a step in which aphotocurable resin (organic material) heated and vaporized to bevapor-like or mist-like is supplied onto an element substrate maintainedat a temperature lower than, or equal to, room temperature and iscondensed on the element substrate, so that the organic material putinto a liquid state is located locally, more specifically, at the borderbetween the side surface of the protruding portion and the flat portionof the surface of the first inorganic barrier layer by use of acapillary action or a surface tension of the organic material. With thisproduction method, the photocurable resin needs to be once vaporized. Inthis case, it is preferred that the photocurable resin does not containa pigment. The viscosity of the photocurable resin, at room temperature(e.g., 25° C.) before the photocurable resin is cured, preferably doesnot exceed 10 Pa·s, and especially preferably is 1 to 100 mPa·s. If theviscosity is too high, it may be difficult to form a thin film having athickness of 500 nm or less.

The production method may further include a step of partially ashing thephotocurable resin layer formed by curing the photocurable resin. Ashingmay be performed by use of a known plasma ashing device, a known ashingdevice using corona discharge, a known photo-excited ashing device, aknown UV ozone ashing device or the like. Ashing may be performed, forexample, by plasma ashing using at least one type of gas among N₂O, O₂and O₃, or by a combination of plasma ashing and ultravioletirradiation. In the case where an SiN film is formed by CVD as each ofthe first inorganic barrier layer 12 and the second inorganic barrierlayer 16, N₂O is used as material gas. Therefore, use of N₂O for ashingprovides an advantage of simplifying the ashing device.

Ashing results in oxidizing the surface the organic barrier layer 14 tomodify the surface the organic barrier layer 14 to be hydrophilic. Inaddition, ashing results in shaving the surface the organic barrierlayer 14 substantially uniformly and forming extremely tiny concaved andconvexed portions to increase the surface area size of the organicbarrier layer 14. The effect of ashing of increasing the surface areasize is greater for the surface of the organic barrier layer 14 than forthe first inorganic barrier layer 12 formed of an inorganic material.Since the surface of the organic barrier layer 14 is modified to behydrophilic and the surface area size thereof is increased, theadhesiveness between the organic barrier layer 14 and the secondinorganic barrier layer 16 is improved.

In order to improve the adhesiveness between the first inorganic barrierlayer 12 and the organic barrier layer 14, the surface of the firstinorganic barrier layer 12 may be exposed to plasma ashing before theorganic barrier layer 14 is formed.

Ashing results in, for example, removing the photocurable resin formedon the protruding portion by the particle P to adjust the locationand/or the volume of the organic barrier layer 14 left in a final state,and also results in improving the adhesiveness between the organicbarrier layer 14 and the second inorganic barrier layer 16.

The method for producing the OLED display device according to anembodiment of the present invention may further include, after the stepof forming the thin film encapsulation structure, a step of opticallyacquiring a pattern of the organic barrier layer 14 and a step ofdetermining whether the thin film encapsulation structure is good or notbased on the pattern. Since the black organic barrier layer 14 isformed, it may be determined whether the thin film encapsulationstructure is good or not based on the pattern of the organic barrierlayer optically acquired. Such an inspection process may be easilyinlined. This improves the yield.

Specifically, a pattern of a region, of the element substrate having thefirst inorganic barrier layer formed thereon, on which the organicbarrier layer (solid portions) is to be formed (such a pattern is alsoreferred to as a “design pattern” or a “target pattern”) is prepared.From the element substrate having the organic barrier layer 14 formedthereon, the pattern of the organic barrier layer (solid portions) isoptically acquired by use of, for example, an image capturing device.The acquired pattern of the organic barrier layer (solid portions) iscompared against the design pattern (target pattern), and thus it isdetermined whether or not the organic barrier layer (solid portions) hasbeen formed in the predetermined region. With the method for producingthe organic EL display device according to an embodiment of the presentinvention, the organic barrier layer is black. Therefore, the pattern ofthe organic barrier layer may be acquired optically with high precision.Naturally, the design pattern does not include a pattern of the organicbarrier layer (solid portions) to be formed in correspondence with theparticles. However, in the case where a pattern matching the designpattern is formed, if the particles are present, it is presumed that theorganic barrier layer (solid portions) corresponding to the particleshas also been formed. Therefore, the yield is improved as compared witha case where no inspection is made regarding the state of formation ofthe organic barrier layer. The determination is made with higherprecision or in a shorter time as compared with a case where atransparent organic barrier layer is formed.

It may also be inspected whether or not an organic barrier layercorresponding to the particles has been formed. For example, foreignobjects on the element substrate are detected by the foreign objectdetection device before the organic barrier layer is formed, and dataincluding position information on the foreign objects (mapping) andimage information on a microscopic region including each of the foreignobjects (light intensity distribution) is acquired. After the organicbarrier layer is formed on the element substrate, a foreign objectinspection is performed in substantially the same manner by use of theforeign object detection device, and substantially the same type of datais acquired. The data before the formation of the organic barrier layerand the data after the formation of the organic barrier layer may becompared against each other to determine whether or not the organicbarrier layer corresponding to each of the particles has been formed.With the method for producing the organic EL display device according toan embodiment of the present invention, the organic barrier layer isblack. Therefore, the image information (light intensity distribution)is significantly changed by the formation of the organic barrier layer.For this reason, the determination is made with higher precision or in ashorter time as compared with a case where a transparent organic barrierlayer is formed.

INDUSTRIAL APPLICABILITY

Embodiments of the present invention are applicable to an organic ELdisplay device, especially, a flexible organic EL display device, and amethod for producing the same.

REFERENCE SIGNS LIST

-   1 flexible substrate-   2 back plane (circuit)-   3 organic EL element-   4 polarizing plate-   10 thin film encapsulation structure (TFE structure)-   12 first inorganic barrier layer-   14 organic barrier layer-   16 second inorganic barrier layer-   30 lead wire-   42 lower electrode-   44 organic layer-   46 upper electrode-   48 bank layer-   50 foreign object detection device-   52 controller-   54 detection head-   60 inkjet device-   62 controller-   64 inkjet head-   66 UV irradiation head-   100 organic EL display device

The invention claimed is:
 1. A method for producing an organicelectroluminescent display device, the organic electroluminescentdisplay device including: a plurality of pixels; an element substrateincluding a substrate, and a plurality of organic electroluminescentelements supported by the substrate and respectively located in theplurality of pixels; and a thin film encapsulation structure coveringthe plurality of pixels, wherein the thin film encapsulation structureincludes a first inorganic barrier layer, an organic barrier layer incontact with a top surface of the first inorganic barrier layer, theorganic barrier layer including a plurality of solid portionsdistributed discretely, and a second inorganic barrier layer in contactwith the top surface of the first inorganic barrier layer and topsurfaces of the plurality of solid portions of the organic barrierlayer, the method comprising a step of forming the thin filmencapsulation structure, wherein the step of forming the thin filmencapsulation structure comprises: step A of preparing the elementsubstrate having the first inorganic barrier layer formed thereon, stepB of forming a liquid film containing a photosensitive resin on thefirst inorganic barrier layer, step C of irradiating the liquid filmwith light to form a resin layer, and step D of forming the organicbarrier layer, the step D including the step of partially removing theresin layer by a dry process, wherein the organic barrier layer isblack, wherein the inclining surface of the first inorganic barrierlayer is lyophilic to the liquid film, and wherein a region enclosed bythe bank layer is repelling against the liquid film.
 2. The method ofclaim 1, wherein the organic barrier layer contains a dye or a pigment.3. The method of claim 1, wherein the inclining surface of the banklayer has an inclination angle smaller than, or equal to, 60 degrees. 4.The method of claim 1, wherein the step D further includes the step ofperforming a plasma process and/or a corona process.
 5. The method ofclaim 1, wherein the step of forming the thin film encapsulationstructure further includes the step of, after the step A and before thestep B, performing ashing on a surface of the first inorganic barrierlayer.
 6. The method of claim 1, wherein the step of forming the thinfilm encapsulation structure further includes the step of, after thestep A and before the step B, supplying a silane coupling agent onto thesurface of the first inorganic barrier layer.
 7. The method of claim 1,wherein the liquid film contains a photocurable resin and a dye or apigment.
 8. The method of claim 1, wherein the liquid film contains aphotopolymerizable dye monomer.
 9. The method of claim 1, wherein thestep B is performed by spraying, spin-coating, slit-coating, screenprinting or inkjet printing.
 10. The method of claim 1, wherein the stepB includes the steps of: after the step A, putting the element substrateinto a chamber and supplying a vapor-like or mist-like photocurableresin into the chamber, and condensing the photocurable resin on thefirst inorganic barrier layer to form the liquid film.
 11. The method ofclaim 1, further comprising the steps of, after the step of forming thethin film encapsulation structure: optically acquiring a pattern of theorganic barrier layer, and determining whether the thin filmencapsulation structure is good or not based on the pattern.